To reduce the size of the front end (and therefore drag) of a sports car to achieve a racing car design and reduce overall mass, the passenger compartment is typically made as small as possible, while at the same time ensuring at least a reasonable degree of comfort and, above all, adequate safety of the occupants in the event of a crash. Conformance with accident safety standards is what normally determines the extent to which the size of the passenger compartment can be reduced, i.e. the most rigid structural parts of the frame are kept as far away as possible from the occupants (in particular, the occupants' heads) to prevent the occupants from striking them in the event of a crash.
Safety standards in the United States (and many other countries, such as Canada and South Korea) require crash testing using instrumented, unrestrained crash dummies (i.e. with no seat belts). In a head-on collision with no seat belt, the occupant is literally hurled towards the front of the car, and is slowed down by the front airbag and the retaining action of the dashboard and seat. The trajectory of the occupant's head as he is hurled forward is one of the main factors governing the design of sports car passenger compartments, by including a horizontal forward component, and an upward vertical component. Which means a cramped (particularly, low-roofed) passenger compartment increases the likelihood of the occupant's head fatally striking the top windscreen cross member (which is a structural and therefore rigid component part of the frame).
At present, the only way of preventing the occupant's head from striking the top windscreen cross member in the event of an unrestrained head-on crash is to increase the vertical distance between the occupant's head and the cross member, i.e. the height of the passenger compartment roof (thus increasing the size of the passenger compartment, in contrast to the above design targets), or to lower (and so reduce the comfort of) the front seat.
Patent Applications WO0071370A1 and US2005080530A1, which are incorporated by reference, describe a road vehicle, in which, to protect the occupants in the event of a crash, the position of the frame with respect to the ground is altered by expanding or contracting the suspensions suspending the frame from the wheels.